The spherical algorithm is NOT the proper way. The UK
National Grid is based on the Gauss-Kruger Transverse
Mercator fully-conformal projection.
Therefore, you:
(1.) MUST use the cartesian algorithm, and
(2.) MUST correct for the scale factor squared. (Length x
scale factor x width x scale f
address is http://www.ordsvy.gov.uk
I hope this is of some help,
regards,
Pete, Ordnance Survey, UK
> -Original Message-
> From: Thake, Peter
> Sent: 23 September 1999 13:52
> To: Davies, Phil
> Subject: FW: MI Area calculations
>
>
> Phil,
> I'd say cart
Hi,
I am using OS data to digitise agricultural field polygons and then obtain their areas
in Mapinfo.
I believe you should use Options/Preferences/Map Window and select the Cartesian
Distance/Area option.
Good luck
Rod Ellis
GIS Unit
ADAS Aberystwyth
Tel 01970 621438
Fax 01970 617798
Email
I have been using the spherical algorithm to calculate the area of field
polygons since upgrading to MI Pro 5.5. Is this the correct way for use with
Ordnance Survey data which is tied in to the British National Grid? The
reason that I ask is because I have been sent and Arc View shape file where
Thanks to all for the suggestions so far. Here's some more information from
further experimenting.
The problem seems to be restricted to objects that cross or touch the 180
degree line in any way. If you click on the triangles and drag them one
pixel away from the 180degree line and the pole, the
gt; Sent: Wednesday, 4 August 1999 12:25
> To: '[EMAIL PROTECTED]'; '[EMAIL PROTECTED]'
> Subject: MI area calculations broken
>
> I have been making comparisons of the area of various objects, and have
> found MapInfo's area calculating function to
Hello Mark,
> I have been making comparisons of the area of various objects, and have
> found MapInfo's area calculating function to be seriously broken, at least
> in some projections (Polar Azimuthal projections).
MapInfo Pro's area calculation is independent of the current map projection. It
I have been making comparisons of the area of various objects, and have
found MapInfo's area calculating function to be seriously broken, at least
in some projections (Polar Azimuthal projections).
Attached is the MB code and an MBX (both are tiny) which demonstrates the
problem. To summarise wha
